Method of refining mineral oils by means of inorganic fluorine compounds



Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE METHOD OF REFININGMINERAL OILS BY MEANS OF INORGANIC FLUORINE COM- POUNDS No Drawing.Application October 25, 1937,

Serial No. 170,975

15 Claims. Our invention relates to the refining of mineral oil by means.of liquid or liquefied inorganic finer-- ine compounds, containingsulfur, which we have discovered to be particularly advantageous for Bpurifying mineral ofls of different boiling ranges and types.

More specifically our invention relates to the extraction of mineraloils by means of sulfur containing inorganic fluorine compounds asselective l solvents, for the purpose of dissolving the aromatic andunsaturated components of the oil and.thereby separating them from theparafiinic type.

Our invention further contemplates the separation of solid parafiinehydrocarbons, or wax, from those which are liquid at low temperature, bythe use of liquid or liquefied inorganic sulfur containing fluorinecompounds in admixture with auxiliary solvents which are miscible in anyproportion with both, the oil to be refined and the selective solvents.

It is well known'in the art that, for example, naphtha fractions arecomposed of groups of components which are respectively designated asaromatic, unsaturated, hydroaromatic or naphthenic, and paramnic.

The hydroaromatic and parafiinic constituents of naphtha fractions aresometimes used as solvents in the cleaning industry, and they are ofcomparatively small value as compared with the olefinic and especiallythe aromatic constituents. These latter two groups of components arewidely used as blending agents of gasolines for the purpose ofincreasing the octane number 5 of motor fuels and also as lacquersolvents and thinners. It is, therefore, important to provide for aprocess which will emciently separate the desirable oil constituentsfrom the undesirable ones, for instance by extraction with selective 40solvents which will dissolve the aromatic and burning 011. Here again itis necessary to separate the saturated from the unsaturated hydrocarbongroups in order to be able to use the respective oil. constituents forthat purpose for which they are most suited.

Likewise in the field of lubricating oils it is generally recognizedthat hydrocarbon groups of low viscosity index and high carbon formingproperties tend to decrease the stability. of the lubricating oil andthat their removal will yield a refined oil of greatly improvedcharacteristics, indicated especially by great resistance to oxidation,by a low carbon residue, and by a high viscosity index.

We have now found that sulfuricoxyfluoride, SO2F2, andsulfurhexafluoride, SFs, are particularly advantageous for separatingthe aromatic and olefinic type of oil components from the paraffinictype of constituents of oil fractions similar to those described above,because these solvents exert a very high degree of selectivity. To thesame group of sulfur containing inorganic fluorine compounds which aresuitable for oil refining in accordance with our invention belong alsodisulfur-difluoride, sulfur-difluoride and sulfur-tetrafluoride. Whereasat least some of the corresponding chlorine derivatives are known to beunstable in presence of mineral oil and react with it chemically, wehave found that the above cited sulfur containing inorganic fluorinecompounds do not decompose and do not form sludge or react otherwisechemically with the hydrocarbon oil to be extracted.

The following examples will further illustrate our invention as so fardisclosed:

Y Example 1 One volume of straight-run naphtha was agitated with onevolume sulfuricoxyfiuoride and Example 2 A transformer oil was treatedwith 10 sulfuricoxyfluoride at +28 C. Two layers were obtained whichwere separated and from which the solvent could be recovered withoutdecomposition of the oil or part thereof.

Example 3 A lubricating oil distillate of '75 viscosity at 210 F. and 28A. P. I. gravity was agitated with an equal volume ofsulfuricoxyfluoride at room temperature. A separation into two phasesoccurred.

Example 4 A dewaxed Mid-Continent overhead cylinder stock wastreatedwith sulfurhexafluoride at 51 C. at a pressure of 570 pounds persquare inch by gauge. Two layers were formed which were separated fromeach other, the rafiinate be,- ing the upper layer. No chem cal reactionbemiscible with the oil.

tween the solvent and rafllnate or extract occurred in this test nor inthe other experiments shown.

Example 5 A Mid-Continent residual oil upon agitation with an equalvolume of sulfuricoxyfluoride at 87 F. showed a separation into twolayers.

In carrying out our extraction process one of the above mentionedinorganic fluorine derivatives may be usedeither alone or in mixturewith one or more of the others.

Our invention is further not limited to the use of one or more of theselective inorganic fluorine compounds. In some instances, especiallywhen extracting heavy lubricating oils, it is of advan tage to carry outthe extraction in the presence of an auxiliary solvent for the purposeof facilitating the extraction and further controlling the extentthereof. Such auxiliary solvents may be selected from the class which ismiscible in any proportion with both the selective solvent and thehydrocarbon oil to be treated, if the solvent power of the selectivesolvent is to be increased. Representatives of this class of auxiliarysolvents are the aromatic hydrocarbons, the non-selective class and fromto 50 volumes per cent selective inorganic" fluorine solvent.

We may also use our selective inorganic fluorine solvents in mixturewith an auxiliary solvent of the class which is miscible in anyproportion with the selective'solvent but substantially im-Representatives of this class are for example the alcohols and theyserve to further increase the selectivity of our selective solvents.

In other instances the presence during the extraction step ofsubstantial volumes of light petroleum fractions such as propane orbutane or the presence of dichloro-difiuoro methane is .of advantage. l

It is further to beunderstoodthat, instead of the batch treating methoddescribed above, also,

the well known counter current operating method may be used, employingtherefor either a tower packed with Raschig rings .or provided withplates, or a mixing and settling tank equipment consisting of three ormore stages.

Qur selective inorganic fluorine solvents are also suitable for dewaxingwhen used inthe Presence of an auxiliary solvent of the class which ismiscible in any proportion with both the oil to be dewaxed and theselective solvent, If such auxiliary solvent is added to a mixture ofwaxy oil and inorganic fluorine solvent the temperature of completemiscibility will be reduced, this reduction depending upon the amount ofauxiliary solvent added. We found that in addbelow substantially all theliquid hydrocarbons but will exert substantially no solvent action onthe solid hydrocarbons. When a wax oil is dissolved in such solventblend at elevated temperature and the solution is thencooled to 09 1'.or below, the solid hydrocarbons will crystalline out and may be removedfrom the dewaxed oil solution by filtering, centrifuging or decanting.

' It'is further to be understood that the extraction step as describedabove may also be combined with the dewaxing in which case the extractedoil, before removal of solvent, is further diluted with a mixture ofselective solvent and auxiliary solvent in the proportions disclosedabove, cooled to 0 1''. or below and subjected to filtration. Likewisethe extraction may follow the dewaxing in which case more selectivesolvent is added to the dewaxed oil solution until at least separationinto two phases occurs.

Obviously modifications and variations of our invention as hereinaboveset forth, may be made without departing from the spirit and scopethereof.

This application is a continuation in part of the application Serial No.23,130 filed May 28, 1935 for Method of refining mineral oils." 4

We claim the following as our invention:

1. A method of refining a mineral oil comprising extracting the oil witha selective solvent pound containing sulfur, to produce a separationinto relatively parafiinic and non-parafiinic'.

phases, separating the phases from each othcr and recovering the solventtherefrom.

2. A method of refining a mineral oil comprising mixing the oil withsulfuricowfluoride as selective solvent and adjusting the temperature toproduce a separation into two oil-containing phases, and separating thephases.

3. A method of refining a mineral oil comprising mixing the oil withsulfurhexafiuoride as 'se-" lective solvent and adiusting thetemperatureto produce a separation into two oil-containing phases, andseparating the phases.

4. A method of refining s. mineral oil compris ing extracting the oilwith a selective solvent con sisting of a liquefied inorganic fluorinecompound containing sulfur, in admixture with an aux-" iliary solvent toproduce a separation-into two relatively paraiiinic and non-paramnicphases, separating the phases from each other and recov-f-- ering thesolvents therefrom.

5. A'method oi'refining a mineral oil compelsing extracting the oil witha selective solvent consisting of a liquefied inorganic fluorinecompound containing in admixture with an auxilia'ry solvent of the classwhich is miscible in any Proportion with both the oil andthe select?solvent to produce a separation into two rell'- I tively paraflinic andnon-parafiinic phases, separating the phases fronr each other andrecovering the solvents therefrom.

6.'A method of refining a mineral oil comprising extracting the oilwitha selective solvent consisting of a liquefied inorganic fluorinecompound containing sulfur, in admixture with an auxiliary solvent ofthe class which is miscible with at least one of the components of themixture of selec-- tive solvent and oil to be extracted to produce aseparation into two relatively parafiinic and V non-parafiinic phases,separating the, phases from each other and recovering the solventstherefrom.

'I.A method of refining s mineral oil comprising extracting the oil withliquefi d sulfuricoxyfiuoride as selective solvent in admixture with anauxiliary solvent to produce a separation into two relatively parafiinicand non-parafllnic phases, separating'the phases from each other andrecovering the solvents therefrom.

8. A method 0:: refining a mineral oil comprising extracting the oilwith liquefied sulfurhexafluoride as selective solvent in admixture withan auxiliary solvent to produce a separation into two phases, separatingthe phases from each other and recovering the solvents therefrom.

9. A method of dewaxing a mineral oil comprising dissolving the oil in amixture containing as a selective solvent, a liquefied inorganicfluorine compound containing sulfur, and an auxiliary solvent of theclass which is miscible in any proportion with both the oil and theselective solvent and in such proportion as not .to produce a separationinto two liquid layers at the dewaxing temperature, cooling the mixtureto below the desired pounpoint, removing the wax therefrom andrecovering the solvents from the dewaxed oil solution and from the wax.

10. A method according to claim 9 in which the selective solvent issulfuricoxyfiuoride.

11. A method according to claim 9 in which the selective solvent issulfurhexafluoride.

12. A method according to claim 9 in which the selective solvent issulfuricoxyfiuoride and the auxiliary solvent is a substance of theclass of benzol and its homologues.

13. A method according to claim 9 in which the selective solvent issulfurhexafiuoride, and the auxiliary solvent is a substance of theclass of benzol and its homologues.

14. A method of producing lubricating oils of high viscosity index andlow pour point comprising extracting the oil in accordance with themethod of claim 1, adding to the raflinate phase so obtained beforerecovery of solvent therefrom, further amounts of the selective solventand an auxiliary solvent of the class which is miscible in anyproportion with the oil and the selective solvent in such proportion asnot to produce a separation into two liquid layers at the dewaxingtemperature, cooling the mixture to below the desired pour point andremoving the wax therefrom.

15. A method of producing lubricating oils of high viscosity index andlow pour point comprising dewaxing the oil in accordance with the methodof claim 9, adding to the dewaxed oil mixture so obtained, beforerecovery of solvent therefrom, a further amount of selective solvent toproduce a separation into phases relatively paraflinic andnon-paraflinic and separating the phases from each other.

ERNST TERRES. JOSEF MQOS. HANS RAMSEB.

